Sieves were obtained from Stokvis/Smit (IJmuiden, The Netherlands). 2.3. Capillary electrophoresis The presently applied CE procedure is based on Dionex Application Note 68 and has been described in detail elsewhere [14]. Briefly, electropherograms were obtained using a Waters Quanta 4000 CE system equipped with a UV detector, a negative power supply and an automatic sample changer.